Recognition of pattern information including a fingerprint is widely used as a means for personal identification, crime prevention and the like. When pattern information is used aiming at biometric identification, it is a common practice to register a pattern first to hereafter execute collation based thereon.
With a conventional pattern information registration method, it is difficult to decide a basis for determining whether pattern information data is adequate or not. There is accordingly a problem that pattern information data failing to satisfy accuracy required of a collation device is registered to result in making identification among data difficult when there is a large volume of data. Thus, with a conventional pattern information registration method, it is impossible to determine whether pattern information data is adequate or not.
Examples of methods which solve such a problem are recited in, for example, Japanese Patent Laying-Open No. 8-263658 and for example, Japanese Patent Laying Open No. 2000-339461.
In the method disclosed in Japanese Patent Laying-Open No. 8-263658, which relates to a fingerprint registration method, a normal feature point and a pseudo feature point of a fingerprint are detected to calculate the number of pseudo feature points approximately centered around the normal feature point within a registration window. Then, pseudo feature points within all the registration windows are summed up and divided by the number of registration windows to obtain an average number of pseudo feature points in the registration window. Since pseudo feature points are feature points generated by cracks, crinkling or the like, the smaller the average number of pseudo feature points is, the more adequate an image quality of a fingerprint image is indicated to be. Accordingly, when the average number of pseudo feature points is not more than a threshold value, determination is made that an image quality of an image of a photographed fingerprint is adequate to execute registration processing.
On the other hand, in the method of Japanese Patent Laying Open No. 2000-339461, which relates to a pattern dictionary generation method, an additional dictionary is generated for reinforcing weak points of a pattern dictionary. When generating an additional dictionary, a feature vector of a learning object pattern and a recognition result are input to obtain a nearby region centered around each feature vector. Here, a nearby region is a set of respective feature vectors satisfying a fixed inclusive condition. As an inclusive condition, it is possible, for example, to set feature vectors within a nearby region to be all erroneously read data. Maximum one of thus obtained nearby regions is obtained and written into the additional dictionary.
Other than the above-described methods, the following methods are disclosed.
The feature extraction device recited in Japanese Patent Laying-Open No. 3-218575 considers information necessary for authentication being obtained when the number of feature points obtained by processing a fingerprint image is not less than a predetermined value and executes registration processing.
The fingerprint collation device recited in Japanese Patent Laying-Open No. 63-4381 considers, when the number of feature points obtained by processing a fingerprint image is not more than a predetermined value, that it is an adequate fingerprint with a small number of pseudo feature points and executes registration processing.
In the fingerprint identification determination method recited in Japanese Patent Laying-Open No. 1-131978, feature points of a plurality of fingerprints taken are collated with each other to register one including numbers of common feature points.
The image collation device recited in Japanese Patent Laying-Open No. 11-154230 collates an image with a template already registered and when high coincidence is obtained, registers the image as a new template.
In addition, one example of a pattern collation device is recited in Japanese Patent Laying-Open No. 2002-288667 which executes collation by using a probability of accidental coincidence when comparing with an arbitrary pattern.
The pattern collation device recited in Japanese Patent Laying-Open No. 2002-288667 collates a graphic form to be examined and a model graphic form by using a probability that feature points are more likely to coincide with each other when an arbitrary graphic form and a model graphic form are compared than when the graphic form to be examined and the model graphic form are compared.
The above-described conventional techniques all have the problems set forth below.
The method of Japanese Patent Laying-Open 8-263658 is a method of determining whether pattern information data is adequate or not based on pseudo feature points. Pseudo feature point is different from a feature point (normal feature point) as data of pattern information itself. Determination whether pattern information data is adequate by the method of Japanese Patent Laying-Open No. 8-263658 is not based on feature points of the pattern information data.
Accordingly, since in the method of Japanese Patent Laying-Open 8-263658, determination of adequacy/inadequacy is made based on a pseudo feature point as information not a feature point, it is impossible to determine adequacy/inadequacy of pattern information data with a feature point as information.
On the other hand, the method of Japanese Patent Laying-Open No. 2000-339461 is a method of reinforcing a weak point of a pattern dictionary and not aimed at determining whether pattern information data is adequate.
In addition, the pattern information registration methods recited in Japanese Patent Laying-Open No. 3-218575, Japanese Patent Laying-Open No. 63-4381 and Japanese Patent Laying-Open No. 1-131978 are not for determining whether pattern information data is adequate or not as will be described in the following.
In other words, the methods of Japanese Patent Laying-Open No. 3-218575, Japanese Patent Laying-Open No. 63-4381 and Japanese Patent Laying-Open No. 1-131978 take the size of a fingerprint into no consideration and take only the number of feature points into consideration. When the number of feature points is not less than a fixed number, these methods determine that it is adequate. These methods, however, are not for determining adequacy/inadequacy of pattern information data because no size of a fingerprint is taken into consideration.
The methods of Japanese Patent Laying-Open No. 11-154230 and Japanese Patent Laying-Open No. 2002-288667 are a template registration method and a method of calculating the degree of similarity between a graphic form to be examined and a model graphic form, respectively, and not for determining whether pattern information data is adequate as well.